Researchers Discover the 2009 Swine Flu Pandemic Originated in Mexico 27 June 2016

Researchers discover the 2009 swine flu pandemic originated in Mexico 27 June 2016 swine Mexican isolates found in this study. The only other H1N1 pandemic flu known to date was the "Spanish" flu of 1918 that killed between 50 and 100 million people—3 to 5 percent of the world's population. Influenza viruses infect up to 500 million people annually. "Knowing where and how an animal influenza virus infects humans and spreads all over the world helps us understand how we can reduce risk of these pandemics," says the study's senior author, Adolfo García-Sastre, PhD, Director of the Global H1N1 virus. Credit: C. S. Goldsmith and A. Balish, CDC Health and Emerging Pathogens Institute, Irene and Dr. Arthur M. Fishberg Chair and Professor of Medicine (Infectious Diseases), and Professor of Microbiology at the Icahn School of Medicine at The 2009 swine H1N1 flu pandemic—responsible Mount Sinai. for more than 17,000 deaths worldwide—originated in pigs from a very small region in central Mexico, Determining the original location of the 2009 swine a research team headed by investigators at the flu, known as an A/H1N1 pathogen, lends a note of Icahn School of Medicine at Mount Sinai is caution to evolving efforts to track problematic reporting. animal and bird viruses, Dr. Garcia-Sastre says. "This virus came from, and was confined to, a very The scientists say their findings, published in the small geographic area and had been there 10 years journal eLife, represent the first time that the origin before one emergent strain gained the capacity to of an influenza pandemic virus has been infect humans," he says. "The virus was completely determined in such detail. under the radar." Researchers used state-of-the-art genetic analysis Dr. Garcia-Sastre directs the Icahn School of to identify the precise location and the main Medicine's Center for Research on Influenza molecular transformations that allowed a pig Pathogenesis, one of five National Institutes of influenza virus to jump into humans. They found Health (NIH) Centers of Excellence for Influenza that the virus responsible was a mix of one North Research and Surveillance. In collaboration with American swine virus that had jumped between the NIH and Avi-Mex, a Mexican veterinarian birds, humans, and pigs, and a second Eurasian company, he and his team obtained 58 whole- swine virus, that circulated for more than 10 years genome sequences from influenza A viruses in pigs in Mexico before jumping into humans. collected in the Mexican pigs and found viral Previously, the most closely related ancestor sequences previously not known to exist in Mexico viruses to the 2009 H1N1 virus were identified in or in any other part of the world. Asian swine, but they were not as close genetically to the human 2009 pandemic H1N1 virus as the Flu viruses have eight mini chromosomes and 1 / 3 when two different strains infect the same cell they cannot ignore small geographic areas with pig farms can exchange genetic segments—a process called —places in which the 2009 pandemic originated and reassortment. "All the pandemic flu viruses that we which the next, perhaps more severe global flu, have tracked have had reassortments," says Dr. may come from." Garcia-Sastre. More information: Ignacio Mena et al, Origins of The 2009 A/H1N1 was also a derivative of two the 2009 H1N1 influenza pandemic in swine in different strains of swine influenza—one that had Mexico, eLife (2016). DOI: 10.7554/eLife.16777 been circulating in Europe and Asia and another that was circulating in the Americas, especially North America. "There is a lot of surveillance in North American pigs, and we know that this virus Provided by The Mount Sinai Hospital was actually a reassortment that occurred years ago between a bird (avian), human and a swine virus," he says. The 2009 swine virus was therefore a "quadruple" reassortment, Dr. Garcia-Sastre says. They also discovered that the parent virus had been present in the pigs in central Mexico for at least 10 years before a strain was generated that could jump into humans, and that the parent strains still exist in the pigs there today. The findings make sense, he says, because the first human flu infections were seen in Mexico before the 2009 pandemic spread rapidly to the United States and then around the globe. "Part of the difficulty in determining origin of pandemic influenzas is that the virus had been silent for so long," he says. "This is true for all previous pandemics. The actual precursors of the viruses are unclear—we know there are reassortments but which ones and where the reassortment took place has been unclear." By solving the origins and the reassortments that led to the 2009 A/H1N1 pandemic, researchers might be able to study existing "brothers and sisters" of the virus to understand the type of mutations needed to allow a virus to jump into humans. Worldwide surveillance of active flu in pigs is crucial because swine are a common global commodity, Dr. Garcia-Sastre says. "We need to monitor the viruses that are circulating, and try to stop mixing influenza strains from different geographic locations," he says. "This study also shows that you 2 / 3 APA citation: Researchers discover the 2009 swine flu pandemic originated in Mexico (2016, June 27) retrieved 27 September 2021 from https://medicalxpress.com/news/2016-06-swine-flu-pandemic- mexico.html This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only. 3 / 3 Powered by TCPDF (www.tcpdf.org).

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